Yes, that's why they are not hankering to get back. It doesn't benefit them. From my ex Bmi colleague I'm told the late flights were a waste of time and ran for the purposes of keeping out the competition
Keeping out what competition? The only potential competitor was already on the route at much higher frequency. BA had 6 daily flights in the last few years of its operation ex BFS and 7 before that in most of the 90's. British Midland had 8 a day, both had 7am departure to LHR (typically give or take 10 mins) and then they had on the half hour, operating alternate hours. BA had a 2145 arrival as standard and a Friday late arrival at 2220., though this later one varied and didn't operate every season. Some Sunday evenings had a later one too.
Besides the argument about what went on then is largely irrelevant. Cost base is immensely different now, competition is different. Fares are different etc.